säteittäisyys

Säteittäisyys, also known as radial symmetry, is a type of symmetry where an organism or object can be divided into similar halves by any plane that passes through its central axis. This means that the organism looks the same no matter which direction it is viewed from, as long as the view is along a line radiating from the center.

In biology, radial symmetry is most commonly found in aquatic animals, particularly those that are sessile (immobile) or drift in the water column. Examples include jellyfish, sea anemones, corals, and starfish. These animals often have a mouth and anus located at the center of their body, with tentacles or other appendages extending outwards in a radial pattern. This arrangement allows them to sense and interact with their environment from all directions, which is advantageous for capturing prey or deterring predators.

The evolutionary advantage of radial symmetry is thought to be its ability to interact with the environment equally from all directions. This is particularly useful for organisms that do not have a preferred direction of movement or feeding. In contrast, bilateral symmetry, where an organism can be divided into two mirror-image halves along a single plane, is typically associated with active movement and directional sensing.

Beyond biology, the concept of radial symmetry can be observed in geometric shapes like circles and spheres, as well as in some man-made designs. It represents a fundamental principle of spatial organization.